An antenna system may include multiple transmission sites. A transmission site may be a base station (also known as a Radio Element Control or a Baseband Unit) or a remote transmission site (also known as a Radio Element or a Remote Radio Head). Transmission sites provide endpoints with wireless network access. Within an antenna system, the transmission sites are distributed among different locations and are generally connected to each other via wired connections (e.g., optical fiber). An antenna system may implement downlink coordinated multi-point processing (DL CoMP). DL CoMP is a special type of multiple-input and multiple-output (MIMO) transmission where multiple transmitting antennas are placed at different transmission sites, while one or more receiving antennas are located at the endpoint. Transmissions from multiple antenna ports at different locations to the same endpoint using the same physical resource blocks (PRBs) are coordinated by the transmission sites. For example, transmissions from multiple base stations may be coordinated over an X2 interface and transmissions involving remote transmission sites may be coordinated over internal fiber connections between a base station and the remote transmission sites.